Textile Materials Conventional Moisture Regain Test Method Composite Fabric Information

Textile materials include textile raw materials processed into textiles and textile semi-finished products, such as various fibers, slivers, yarns, fabrics, etc. The hygroscopicity of textile materials is an important characteristic related to material performance and processing technology. The hygroscopicity of textile materials is usually expressed by the moisture regain rate and the official moisture regain rate of textile materials. These basic quality indicators play a very important role in the commercial trade, performance testing and textile processing of textile materials. Common moisture regain test methods for textile materials Test methods (1) direct measurement method (2) indirect measurement method.
Moisture regain and official moisture regain: The moisture regain of textile materials is the percentage of the amount of water absorbed in the sample to the dry weight of the sample. The moisture regain of textile materials varies from time to time, as does their weight. In order to eliminate weight differences caused by different moisture regains and meet the needs of textile material trade and inspection, the country has stipulated corresponding standards for the moisture regain of various textile materials, called the official moisture regain, which is numerically close to the standard temperature and humidity Equilibrium moisture regain measured under conditions. It should be noted that the regulations on the official moisture regain rate of textile materials in various countries are often based on their own actual conditions, so they are not completely consistent.
There are many methods for testing the moisture regain of textile materials:
(1) Direct measurement method: first weigh the sample, then remove the moisture, then weigh the dry weight of the sample to calculate the actual moisture regain. Depending on the method of removing moisture, direct measurement methods include: oven method, infrared radiation method, high-frequency electric field heating method, vacuum drying method and hygroscopic agent drying method. The oven method and infrared radiation method are often used in industrial production. The advantage of the oven method is that the measurement results are more accurate, but the disadvantage is that it is slow and has low efficiency. The advantages of the infrared radiation method are fast speed, high efficiency, and energy saving. The disadvantages are that the temperature is difficult to control and the measurement results fluctuate.
　(2) Indirect determination method: It uses the relationship between certain properties of the fiber and the moisture regain to indirectly estimate the moisture regain of the fiber. The advantages of this method are fast speed and high efficiency, but the determination of the relationship between fiber-related properties and moisture regain still requires the use of a direct method. Indirect methods can be divided into resistance method, capacitance method, infrared absorption method and microwave method. In China, the resistance method is often used to measure the moisture content of raw cotton. The microwave method has the characteristics of rapid, continuous, non-contact and non-destructive. It can be used for continuous measurement and automatic control. It is a new technology that is still developing recently.
Introduction to the commonly used oven method: It uses resistance heating in the oven to bring the temperature of the air in the oven to a certain value, and maintains this temperature throughout the drying, and then weighs the wet weight of the textile material. The sample is placed in a constant temperature oven for drying, so that the moisture in the textile material continuously evaporates into the hot air, and the exhaust device of the oven is used to continuously discharge the hot and humid air out of the box, creating conditions for the continuous evaporation of the moisture contained in the textile material. . As the moisture contained in textile materials continues to evaporate and lose, the weight continues to decrease. When the weight is dried until it remains unchanged, it is the dry weight of the textile material. At this time, the dry weight of the sample can be obtained by using the method of thermal weighing in the box. Finally, the moisture regain of the textile material can be obtained based on the wet weight and dry weight of the sample. In the oven method, the drying temperature is specified as 105℃±3℃ for cotton; 105~110℃ for wool and most chemical fibers; and 140~145℃ for silk. The drying time is generally 90 minutes.
In addition, the moisture regain of textile materials can also be measured by the resistance wet method. The resistance wet method is based on the different resistivities of textile materials at different moisture regains, thereby measuring the moisture contained in textile materials. For commodities with unstable dry moisture content, such as wool, raw silk, cotton, etc., in order to accurately calculate the weight of such commodities, the method of calculation based on metric (Conditioned weight) is usually adopted internationally, that is, the actual moisture regain (moisture content) of the commodity is measured. rate) to calculate the clean weight of the product, and then convert it into the weight of the public moisture regain rate. The calculation formula is as follows: Common quantity = [actual weight of the product/(1 + actual moisture regain)] ╳ (1 + official moisture regain) = clean weight of the product ╳ (1 + official moisture regain)
Official moisture regain of major textile fibers:
Cotton: official moisture regain rate: 8.5%
Polyester: official moisture regain rate: 0.4%
Ramie: official moisture regain rate: 13%
Nylon: official moisture regain rate: 4.5%
Wool: official moisture regain rate: 15-16%
Vinylon: official moisture regain: 5%
Silk: official moisture regain: 11%
Acrylic: official moisture regain: 2%
Viscose: official moisture regain: 13%
Polypropylene: official moisture regain: 0%
Acetic acid: official moisture regain: 7%
Chloropropylene: official moisture regain: 0%
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